1. Field of the Invention
The invention relates to a work-sheet feed device for a sewing apparatus provided with a cylinder bed or beds and, in particular, to such a work-sheet feed device in which a holder support supporting a frame holder to which a work-sheet holding frame is attached is coupled to a carrier for moving the holder support, via a coupling mechanism that serves to dampen or isolate vertical vibration transmitted from the sewing apparatus, and reduce vibration or noise upon collision of the work-sheet holding frame with the cylinder bed, without affecting stitches formed on a work sheet mounted in the work-sheet holding frame.
2. Description of the Related Art
A known example of a work-sheet feed device for an industrial sewing apparatus for forming sewing patterns or embroidery patterns is disclosed in U.S. Pat. No. 5,887,536, that is assigned to the same assignee as the present application. In this example, an X movable frame extends in the X direction, or lateral direction, perpendicular to cylinder beds of a multi-head embroidering machine equipped with three embroidering devices or units, and a Y-direction feed mechanism is provided for moving the laterally opposite end portions of the X movable frame in the Y direction. Also, an X-direction feed mechanism is provided on a second movable frame of the X movable frame, for moving an X carriage in the X direction, and a coupling plate is provided for coupling the X carriage to a first movable frame that extends in the lateral direction. In addition, a pair of left and right frame holders that support a work-sheet holding frame for a cylindrical object are attached to the first movable frame so that the work-sheet holding frame can be moved by the X-direction and Y-direction drive mechanism in the lateral (left-to-right) direction and front-to-back direction.
In the work-sheet feed device as disclosed in U.S. Pat. No. 5,887,536, the driving force of a sewing motor is applied to needle bars of the respective embroidering devices through a main drive shaft, so as to drive the needle bars at the same time in the vertical direction, and a presser foot for embroidering, provided in each embroidering device, is driven in the vertical direction in concert with the needle bar. As a result, vertical vibration caused by the vertical movement or oscillation of the needle bars and presser feet is transitted from a main body frame to the second movable frame or X carriage, and futher to the work-sheet holding frame via the first movable frame or frame holder, whereby the work-sheet holding frame itself vibrates in the vertical direction.
Where work-sheet feed operations are repeatedly performed in the same sewing direction at substantially the same feed pitch, or the work-sheet holding frame is used for a cylindrical object and thus supported only at one end portion thereof, the main body is liable to resonate, thus increasing the vertical vibration. In particular, the vertical vibration of the work-sheet holding frame may be further increased depending upon the sewing speed, resulting in increased noise occurring upon collision of the work-sheet holding frame with the cylinder bed located underneath. In addition, the work sheet mounted in the work-sheet holding frame undergoes vertical vibration, which tends to cause poor thread tightening, stitch skipping, or even thread breakage.